U.S. patent number 4,674,543 [Application Number 06/675,575] was granted by the patent office on 1987-06-23 for tube having an armoring consisting of a plurality of wires.
This patent grant is currently assigned to Kabelmetal Electro Gesellschaft mit Beschrankter Haftung. Invention is credited to Friedrich Schatz, Gerhard Ziemek.
United States Patent |
4,674,543 |
Ziemek , et al. |
June 23, 1987 |
Tube having an armoring consisting of a plurality of wires
Abstract
In the case of strand-shaped material, for instance corrugated
tubes, electric cables or lines, there is provided on the surface
of the material an armoring comprising a plurality of wires which
are applied with a long length of lay and are held by a further
armoring layer. The wires are applied to the material with changing
direction of lay. The additional armoring layer is at least one
wire applied with a short length of lay and which is applied with
initial tension onto the first armoring layer.
Inventors: |
Ziemek; Gerhard (Langenhagen,
DE), Schatz; Friedrich (Langenhagen, DE) |
Assignee: |
Kabelmetal Electro Gesellschaft mit
Beschrankter Haftung (Hanover, DE)
|
Family
ID: |
25816304 |
Appl.
No.: |
06/675,575 |
Filed: |
November 28, 1984 |
Foreign Application Priority Data
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Dec 9, 1983 [DE] |
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3344544 |
Dec 21, 1983 [DE] |
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3346169 |
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Current U.S.
Class: |
138/153; 138/122;
138/132; 138/140; 138/173 |
Current CPC
Class: |
H01B
13/26 (20130101); H01B 7/226 (20130101) |
Current International
Class: |
H01B
7/18 (20060101); H01B 13/26 (20060101); H01B
7/22 (20060101); H01B 13/22 (20060101); F16L
009/04 (); F16L 009/18 () |
Field of
Search: |
;138/129,132,133,144,134,153,172,174,173,DIG.5,122,121,140
;74/51P |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bryant, III; James E.
Attorney, Agent or Firm: Farber; Martin A.
Claims
We claim:
1. In a tube having an armoring, said armoring comprising a first
and a further armoring layer, said first armoring layer having a
plurality of armoring wires lying on the surface of said tube, said
armoring wires being applied with a long length of lay and being
held by said further armoring layer, the improvement wherein
the armoring wires of the first armoring layer each have an
alternating clockwise and counterclockwise rotational directions of
lay on said tube with respect to a longitudinal axis of the tube
viewed in transverse cross-section, and
the further armoring layer comprises at least one holding wire
having a short length of lay which is placed with initial tension
over the first armoring layer.
2. The tube having an armoring according to claim 1, wherein
the first armoring layer has an angle of wrap less than
360.degree..
3. The tube having an armoring according to claim 2, wherein
the angle of wrap of the first armoring layer is less than
180.degree..
4. The tube having an armoring according to claim 1, wherein
said armoring wires cover at least 50% of the surface of the
tube.
5. The tube having an armoring according to claim 1, wherein
said further armoring layer comprises a single said holding wire
having said initial tension just below the yield point of said
holding wire.
6. The tube having an armoring according to claim 1, further
comprising
an extruded plastic jacket applied over said armoring layers.
7. The tube having an armoring according to claim 1, further
comprising
a second armoring layer is arranged over and with opposite
direction of lay with respect to said first armoring layer, and
wherein
both said first and second armoring layers are fixed in common by
said at least one holding wire.
8. The tube having an armoring according to claim 1, wherein
said tube having a wall thickness and the diameter of the armoring
wires corresponds approximately to the wall thickness of the
tube.
9. The tube having an armoring according to claim 1, wherein
said tube having a helical corrugation, and wherein
said holding wire has a length of lay which corresponds
approximately to the pitch of the corrugation, and the holding wire
rests in the region of valleys of the corrugations of the tube on
the first armoring layer and presses the first armoring layer into
the valleys of the corrugation.
Description
FIELD AND BACKGROUND OF THE INVENTION
The invention concerns strand-shaped material, for instance a
tubular metallic structure with helical or annular corrugations or
an electric cable or an electric line having an armoring which
consists of a plurality of wires resting on the surface of the
material, which are applied with a long length of lay and are held
by a further armoring layer.
Corrugated tubes have the advantage of being both flexible and
transversely rigid. Their disadvantage is that when subjected to
load by internal pressure they, lengthen in longitudinal direction
at first elastically and then plastically, even under slight
pressures. It is known to eliminate this disadvantage by placing a
braiding around the corrugated tube. The braiding restrains the
longitudinal lengthening and, as a result, makes the tubes somewhat
more resistant to pressure. Braiding machines are, however, very
slow and are extremely expensive, particularly for tubes of large
diameter.
From British Patent No. 1 336 630 a corrugated tube is known which
is reinforced by a plurality of armoring wires applied with a long
length of lay. Over the first armoring layer there is a second
armoring layer, also applied with a long length of lay and
advantageously applied in the direction opposite to the direction
of lay of the first armoring layer. The advantage of this known
construction is that as a result of the armoring layers the
corrugated tube can take up substantially higher pressures than
previously without lengthening as a result of the internal
pressure. The disadvantage of the known conduit is that the method
of applying the armoring wires is very expensive, particularly when
tubes of large diameter are to be armored. Upon the manufacture of
such tube it is necessary that the reels which hold the individual
armoring wires travel around the longitudinal axis of the traveling
corrugated tube.
From Federal Republic of Germany OS No. 27 05 743 it is known to
apply a layer of wires onto the surface of an electric cable. Such
layers of wires serve, in the cable art, as concentric ground or
neutral line. Upon the production of such layers, the layer of wire
is held, after application onto the surface of the cable, by a
strap which may consist, for instance, of plastic or else of
metal.
One important advantage of such a cable provided with a ground or
neutral line is that upon the production of a junction point merely
the conductor and the insulation need be cut while the ground or
neutral conductor can be easily removed from the surface of the
cable and remains uncut. Such a technique is known, for instance,
from Federal Republic of Germany Utility Model GM No. 18 75 570. It
is therefore absolutely necessary that the layer of wire be movable
in axial direction. To this extent the known layer of wire cannot
be considered an armoring layer which is intended to take up
tensile forces.
The object of the present invention is to provide a strand-shaped
material which can take up high tensile forces and can be
manufactured economically, particularly also in large
diameters.
SUMMARY OF THE INVENTION
The object of the invention is obtained by applying wires of a
first armoring layer with alternating direction of lay onto the
material and a further armoring layer comprises at least one
holding wire applied with a short length of lay which is laid onto
the first armoring layer with initial tension. Due to the fact that
wires of the first layer are applied in alternate direction of lay,
the armoring wires can be taken from stationary reels. One can
therefore operate with a very simple cabling device. As a result of
the holding wire which is applied with a short length of lay, the
individual wires of the first armoring layer are held firmly
tensioned on the material, so that an increased frictional lock is
produced which results in the ability to withstand high tensile
stress and, in the case of a corrugated tube, avoids elongation of
the corrugated tube. The decisive factor for the action of this
simple, economical reinforcement is, essentially, the force or
initial tension with which the holding wire is applied. The angle
of the armoring layer with respect to the longitudinal axis of the
corrugated tube is also of importance. An angle of 5.degree. to
45.degree. has been found advantageous in practice. The effect of
this reinforcing layer improves as the angle with respect to the
longitudinal axis decreases. To be sure, the lower limit of the
angle is determined by the required flexibility of the
material.
In the case of electric cables, the holding wire produces an
intimate bond between the electric cable and the armoring layer. It
has suprisingly been found that the flexibility of a cable armored
in accordance with the invention is not substantially reduced by
the armoring layer.
In accordance with one particularly advantageous embodiment of the
invention, the angle of wrap of the first armoring layer is less
than 360.degree. and preferably less than 180.degree.. The armoring
wires should be present in such number that they cover at least 50%
of the surface of the material. This is important, in particular,
in the case of tubes if--as is advantageous in accordance with
another concept of the invention--the diameter of the wires
corresponds approximately to the wall thickness of the tube. As the
further armoring layer there is used merely one holding wire which
is applied with an initial tension which is just below the yield
point of the wire. By this measure the armoring wires are pressed
firmly against the surface of the material and thus increase the
frictional force between the material and the armoring wires. In
the event that the material is a tube and has a helical corrugation
it is advisable to apply the holding wire with a length of lay
which corresponds approximately to the pitch of the corrugation.
This wire should then rest on the armoring layer in the region of
the valleys of the corrugations of the tube and press the armoring
layer into the valleys of the corrugations. In addition to the
force-lock applied by the initial tension there is also produced in
this manner a form-lock between the armoring wires and the surface
of the corrugated tube. An extruded outer jacket of plastic can
also be applied onto the armoring layer.
It is also possible to apply over the first armoring layer a second
armoring layer having the opposite direction of lay and to hold the
two armoring layers and press them onto the material and against
each other by a common holding wire which rests on the second
armoring layer.
The invention furthermore concerns a method of manufacturing
strand-shaped material which is characterized by the fact that a
plurality of wires are applied with long length of lay onto the
strand-shaped material, distributed uniformly on the circumference
of the tube, that the direction of lay is continuously changed, and
that immediately after the placing on of the wires they are fixed
by a holding wire which is applied with a relatively short length
of lay. It is essential in this connection that the holding wire is
wound-on immediately after the applying of the armoring wires onto
the material, in order to provide assurance that the armoring wires
lie in the desired form on the material.
In accordance with a further development of the method of the
invention, over the first layer of wire there is applied a second
layer of wire whose direction of lay is opposite to the direction
of lay of the first layer of wire and the two layers of wire are
jointly fixed by the holding wire. By this measure the tensile
strength of the material can be substantially increased. The layer
of wire, or both layers of wire, are applied, to particular
advantage, with a wrap of less than 360.degree. and preferably less
than 180.degree.. It is also essential that the angle at which the
armoring layer is applied to the surface of the materal be not
greater than 45.degree. to the longitudinal axis of the material at
any place. If the angle is selected larger than this, then there is
a smaller component of force in the longitudinal axial direction.
This would lead to a reduction in the tensile forces which can be
transmitted. The holding wire is applied, to particular advantage,
with a pitch which is smaller than the diameter, and preferably
smaller than half the diameter, of the strand-shaped material.
Since the frictional force between the holding wire and the
armoring layer and thus between the armoring layer and the surface
of the strand-shaped material is applied by the holding wire and
acts essentially only in the region of the holding wire, this
measure also acts to increase the tensile strength.
The invention also concerns an apparatus for the carrying out of
the method for the manufacture of armored corrugated tubes, the
apparatus consisting, according to the invention, of a tube
manufacturing machine which shapes a longitudinally entering metal
strip continuously into a tube and welds its longitudinal seam, a
corrugating device arranged behind same which corrugates the welded
tube, a cabling device which applies the first armoring layer with
alternating direction of lay, a central spinner which applies the
holding wire, and an extruder. The cabling device consists of a
plurality of reels, mounted fixed in space, for the armoring wires
as well as a perforated disk which is driven with alternating
direction of rotation.
In order to apply the wire with the necessary initial stress, the
storage reel for the wire is driven in the direction opposite to
the direction of unwinding. The driving force should be so large
that the necessary initial tension can be produced in the wire.
BRIEF DESCRIPTION OF THE DRAWINGS
With the above and other objects and advantages in view, the
present invention will become more clearly understood in connection
with the detailed description of preferred embodiments, when
considered with the accompanying drawings, of which:
FIG. 1 is a diagramatic side view of a strand-shaped material in
practice of the invention;
FIG. 2 is a diagramatic partial side view of an alternative
embodiment;
FIG. 3 is a diagramatic side view of an apparatus in practice of
the invention; and
FIG. 4 is a graphical representation of the advantageous effect of
the armoring of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the description of the figures, reference is to corrugated
tubes. However, it applies similarly to electric cables and
lines.
FIG. 1 shows a helically corrugated metal tube 1 on whose outer
periphery of plurality of armoring wires 2 are uniformly
distributed. The armoring wires 2 are applied with a relatively
long length of lay, i.e. at a small angle to the longitudinal axis
of the tube 1. At the points of inflection 3 the direction of lay
of the cabling changes. The armoring wires 2 are held in position
by a holding wire 4 which is applied helically over the armoring
wires 2 with a relatively short length of lay. In order that the
armoring wires 2 can prevent lengthening of the corrugated tube 1
when it is acted on by internal pressure, it is necessary that the
armoring wires 2 lie firmly against the surface of the tube. For
this purpose, the holding wire 4 is applied with a large initial
tension which is preferably just below the yield point of the wire.
Due to this large pressing force, the friction between the
corrugated tube 1 and the armoring wires 2 is increased. A plastic
jacket 5, preferably of polyethylene, is extruded to surround the
assembly. The diameter of the armoring wires should correspond
approximately to the wall thickness of the corrugated tube 1.
Depending on the outside diameter of the corrugated tube 1, the
wall thickness is between 0.5 and 2 mm. The diameter of the holding
wire 4 may be of the same order of magnitude, but should advisably
be somewhat larger.
FIG. 2 shows a particularly advantageous embodiment of the
invention. In this case the corrugated tube is also helically
corrugated. The armoring wires 2 are applied in the same manner as
in FIG. 1, but the holding wire 4 is applied with a length of lay
which corresponds to the pitch of the corrugated tube 1. The
holding wire 4 lies in the region of a corrugation valley, so that,
due to its initial tension, it reshapes the armoring wires 2 around
the corrugation peaks of the corrugated tube 1. In this way, in
addition to the friction lock caused by the initial tension, there
is also a form-lock which, in the same way as the friction-lock,
prevents the corrugated tube 1 from elongating when acted on by
internal pressure.
The manufacture of the tubular structures shown in FIGS. 1 and 2 is
effected in the manner that, as shown in FIG. 3, the corrugated
tube 1 which emerges from a tube welding and corrugating device
(not shown) is wrapped with the armoring wires 2 by means of a
cabling device 6. The cabling device 6 consists of a stationary
perforated disk 7 and another perforated disk 8 which is driven
with alternating direction of rotation. The larger the angle of
wrap of the armoring wires 2 with respect to the corrugated tube 1,
the greater the distance between the perforated disks 7 and 8 must
be. With a large distance between the perforated disks 7 and 8, it
is advantageous to provide between the perforated disks a tube
having a somewhat smaller diameter than the diameter of the circle
of holes and to fasten said tube to the perforated disk 7. The
armoring wires coming from the perforated disk 8 are placed by
means of a so-called cabling nipple 9 onto the surface of the
corrugated tube 1 and are fixed directly behind the cabling nipple
9 by the holding wire 4. For this purpose there is used a so-called
central spinner 10 which conprises a rotating laying arm 11 as well
as a mount for the supply reel 12. In order to apply the necessary
initial tension for the holding wire 4, the supply reel 12 is
driven in direction opposite the direction of unwinding, in the
manner that even upon a decrease in the diameter of the layers of
wire on the supply reel 12 the force of removal and thus the
initial tensioning of force for the holding wire 4 is at all times
constant. The armored corrugated tube 1 emerging from the winding
device 10 is then provided, by means of an extruder with the
plastic jacket 5, in a manner not shown in the drawing.
The advantageous effect of the armoring of the invention will be
made clear on basis of the graph shown in FIG. 4. The pressure is
plotted on the abscissa and the change in length per mil is shown
on the ordinate. The curve A shows the elongation of a corrugated
tube of alloy steel having an inside diameter of 140 mm, an outside
diameter of 180 mm, and a wall thickness of 0.3 mm. The corrugation
pitch was 4 mm. It can clearly be seen that this unarmored
corrugated tube lengthens even at relatively low pressures. The
curve B shows the course for a similar corrugated tube which has
been provided with a wire armoring consisting of 40 individual
wires of 0.5 mm which lay on the surface of the tube with a length
of lay of 200 and an angle of wrap of 210.degree.. The holding wire
4 had a diameter of 0.5 mm and was applied with a pitch of 6 mm. It
can clearly be seen that the elongation is substantially less than
in the case of the unreinforced corrugated tube. A similarly
prepared corrugated tube was loaded step-wise with pressure,
pressure relief being effected after each step. The behavior of the
tube tested in this manner is shown in Curve C. Here it can clearly
be seen how large the elastic portion of the elongation (vertical
portion of the curve C) is in each case.
The applied wires 2 can prevent the tube or cable 1 from
lengthening in longitudinal direction and thus increase the tensile
strength only with the component thereof which acts in the
longitudinal direction, i.e. the smaller the angle of the wires to
the longitudinal axis of the cable or tube 1, the greater is their
effect. However, it must be noted that the wires 2 cannot extend
parallel to the longitudinal axis of the cable or tube 1 since in
such case they would be stretched or bulged upon bending. The
larger the angle between the wires 2 and the longitudinal axis of
the cable or tube 1, the smaller is the component of force acting
in the longitudinal direction. The optimum with respect to tensile
strength and flexural strength of the cable or tube 1 is between
15.degree. and 25.degree..
Without the holding wire 4, the wires 2 cannot transmit any forces
since they are not connected to the surface of cable or tube 1. The
connection is produced by the holding wire 4 which is wrapped
around the wires 2 with the smallest possible pitch. The force with
which the wire 4 is wrapped is of controlling importance. From this
force there results, namely, the perpendicular force necessary for
the friction between the wires 2 and the cable or tube 1. For the
force which can be taken up in longitudinal axial direction there
is a dependence on the following factors:
1. number of wires;
2. angle formed by the wires to the axis of the cable or tube;
3. diameter of the wires;
4. coefficient of friction between the wires and the cable or
tube;
5. coefficient of friction between the holding wire and the
armoring wires; and
6. tensile force of the holding wire.
These factors must be optimized in accordance with the purpose of
use.
For many purposes of use it may be advisable to provide between the
surface of a cable and the armoring layer of the wires a metal
tape, preferably of copper, which contacts the individual wires to
each other. In this case, the armoring layer would also produce
electric shielding at the same time.
By means of the invention it is possible substantially to improve
the mechanical properties of a corrugated tube or a cable without
its flexibility being substantially reduced.
* * * * *